1. Field of the Invention
The present invention relates to a boring tool having a detachable cutting blade, and, more particularly the present invention relates to a gun drill for boring holes to extremely exacting tolerances.
2. Description of the Prior Art
A conventional gun drill comprises an elongate shank having a cylindrical cutting head on the end thereof. The head has a front end and a cylindrically shaped outer surface and includes a V-shaped groove for removing chips extending longitudinally rearwardly from the front of the head and is open radially to the outer surface thereof. The cutting head of the gun drill has a cutting blade brazed into a recess in one of the surfaces of the V-shaped groove. The cutting blade is made of carbide or some other hard material which is suitable for cutting steel. An example of a gun drill having a cutting head of the type described above is disclosed in U.S. Pat. No. 3,153,356.
In the manufacture of a conventional gun drill, the carbide cutting blade is brazed into a recess in a surface of the V-shaped chip groove. During brazing, the blade is heated to an elevated temperature and then cooled, which is believed to result in deterioration of the useful life of the blade, that is, the blade material softens and the blade dulls more quickly during use. Further, as the drill is used, the cutting blade becomes worn and requires resharpening. After the cutting blade is sharpened several times, it becomes worn to the point wherein the entire gun drill must be discarded or returned to the manufacturer for retipping with a new cutting head. Other boring tools having a detachable cutting blade or a detachable tip are disclosed in the following patents:
______________________________________ U.S. Pat. No. Inventor ______________________________________ 339,544 S. P. Graham 492,733 H. Meister 752,863 O. P. Roberge 923,257 O. Fredrickson 1,929,801 F. E. Berry 2,310,992 J. R. Proksa 2,451,922 A. J. Cox 3,135,522 W. Bellz 3,289,273 G. P. Artaud 3,304,816 L. C. Galorneau 3,618,962 J. R. Cox et al 3,859,700 Richard R. Jilbert 4,060,335 Holloway et al 4,146,240 Mogens B. Nielsen 4,232,985 Mogens B. Nielsen French Pat. No. 1,274,017 M. Kleine ______________________________________
It is an object of the present invention to provide a boring tool, also referred to as a gun drill, having a detachable cutting blade. More particularly, it is an object of the present invention to provide a cutting blade that may be removed from the head of the boring tool, sharpened and then replaced, or replaced with another blade. It is a further object of the present invention to provide a blade that is capable of being moved forwardly so that the blade may be repeatedly sharpened and then advanced thereby extending its useful life.